In a changing climate, will fire make a bigger run in Western Washington forests?

Originally published September 4, 2018 at 6:00 am
Updated September 5, 2018 at 11:00 am

A research team studying the impact of the 2017 Norse Peak fire cautions that tactics used to reduce fire risk east of the Cascades are not likely to work as well in west-side forests, which are forecast to burn more often.

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GREENWATER, Pierce County — On a remote ridge, the hemlock, silver and noble firs stood for several centuries, nurtured by deep winter snow and drenching rains. Then last year, amid the searing August temperatures, the Norse Peak fire on the east side of the Cascades pushed over the range’s crest and engulfed this stand, killing most of these trees.

Now the charred trunks rise like ghostly sentinels in a forest littered with charcoal, which still gives off whiffs of the smoke that billowed from the 55,909-acre blaze. This austere burn zone is a typical aftermath to intense fires that, over the course of centuries, periodically feast upon the huge amounts of wood that grow in the west-side forests of our region.

The fire ecology of such forests, and how it may evolve amid climate change, is of increasing importance as wild-land smoke emerges as a regional concern. The polluted air that hung this summer over a vast stretch of the West Coast — from San Francisco to Vancouver, B.C. — has generated a fresh wave of support for more logging and cool-season burns to thin the forests and reduce the potential fuel.

These tactics are standard practice east of the Cascades. But in a peer-reviewed paper published this year, a research team of University of Washington, state Department of Natural Resources and U.S. Forest Service scientists caution that such tactics won’t do much to tame or head off west-side fires, which are forecast to happen more often — and burn more acreage — as climate change spurred by the combustion of fossil fuels reduces winter snowpack and increases summer temperatures.

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“We can think of the Norse Peak fire as a kind of tip of the iceberg of what these fires have been in the past and will be in the future,” said Brian Harvey, a University of Washington forestry scientist and one of six co-authors of the fire-science article “Nature of the Beast” that appeared in the March 2018 edition of the journal Ecosphere.

Harvey is working with graduate students and some of his colleagues to set up research sites within the boundaries of the Norse Peak fire zone to assess what happened to the forest. This is part of a larger effort to survey burn zones across the Northwest, and involves laying out circular plots, each 30 meters in diameter, and taking all kinds of measurements ranging from how much the fire charred the trees to the impact on soils.

Harvey is a recent arrival at the UW, a 37-year-old assistant professor whose earlier research focused on tree regrowth after fires in more arid forests in Montana and Wyoming.

The findings, detailed in a study that he led, show that trees had yet to return to some of the driest edges of burn zones, which were dominated by shrubs and grasses. In other areas, trees did take root, but there were fewer of them than in moister, cooler times.

Life on the west side

After moving to Washington in 2017, Harvey steeped himself in the very different dynamics of the rainy west-side forests, teaming up with colleagues that include Jerry Franklin, an 82-year-old UW professor whose research back in the 1970s — as a Forest Service scientist — documented the ecological values of old-growth forest during an era of widespread federal lands logging.

Early in his career, Franklin also delved into wild-land fires. He co-authored a 1982 study of Mount Rainier National Park that uncovered evidence of huge conflagrations 900 years ago that affected nearly 50 percent of the forested areas.

Franklin studied more recent fire history, including the 1902 Yacolt Burn that killed 38 people as it raged through more than 238,000 acres of Western Washington’s Clark, Cowlitz and Skamania counties, engulfing Seattle and the rest of the Puget Sound region in smoke.

UW researcher Jerry Franklin, at age 82, has spent decades studying the old-growth forests of the Pacific Northwest. Here, with research colleague Joshua Halofsky, he looks over the impact of the Norse Peak fire. (Steve Ringman/The Seattle Times)

Last week, Franklin was back in the west-side woods, wielding a trekking pole for balance as he scrambled with Harvey through a sooty section of the Norse Peak burn. They were joined by state Department of Natural Resources researcher Joshua Halofsky, who along with Daniel Donato, another state forestry scientist, were the two lead authors of the Ecosphere article.

Most of the trees Franklin spotted that day were higher-elevation softwood species that — due to their thin bark — can easily be killed by a fire’s heat. Amid a graveyard of big old trees, they spotted a tiny survivor, a stubby short hemlock just a few feet tall that had taken root in a dank spot the fire passed over. It was a rare find in a forest floor, thick with brown needles and scant signs of new greenery.

Unlike many fires started by humans, lightning ignited the Norse Peak fire on Aug. 11 last year. By early September, more than 300 firefighters were working to contain the blaze, which prompted the evacuation of Crystal Mountain ski resort as well as the residents of Gold Hill and Pick Handle Basin.

The burn zone offers stark evidence of the impact of fire in a west-side forest.

But Franklin says it would not make much sense to transfer the east-side strategies of thinning forests to these wetter lands west of the Cascades.

On the east side, in forests dominated by thick-barked ponderosa pine, low-intensity fires in centuries past often came every five to 30 years, clearing out brush and small trees. In the 20th century, decades of human intervention, in the form of fire suppression, sometimes squelched that natural fire cycle, allowing big buildups of fuel. In recent years, restoration efforts are aimed at bringing those forests back to a more natural balance.

But wetter forests, such as the stand torched in the Norse Peak blaze, have a very different relationship with fire. They burn infrequently but the toll on the trees often is severe. Trying to head off these fires would require thinning these public lands every decade or so, and that would change the natural character of these lands in what Franklin calls a “fool’s exercise.”

There also are benefits to these west-side fires, which Franklin says can act as powerful sources of forest renewal.

Many of the fir trees in this forest stand have thin bark and are less able to fend off fire than the thick-bark ponderosa pine that grows east of the Cascades. (Steve Ringman/The Seattle Times)

Within the Norse Peak burn zone, some of the dead trees eventually will topple. Many more will gradually drop off pieces of their trunks until only short snags remain.

More sunlight will reach the forest floor. That will usher in a spectacularly productive few decades of the forest cycle, when a profusion of plants and shrubs such as huckleberries will provide nourishment for mammals, reptiles and amphibians.

“It’s going to take 30 years before you begin to get significant tree canopy closure,” Franklin said. “We will have an incredible diversity of plant life here, which means we will have an incredible diversity of foods. … It’s going to be a buffet.”

Plenty to study

The past 50 years have been a relatively quiet period for fire in the west-side forests. That is expected to change during what scientists forecast to be a tumultuous century for the climate.

Climate scientists have come up with a range of predictions for just how much hotter the Northwest summers will get and how much the winter snowpack will shrink. One big unknown in these forecasts is the scale of global fossil-fuel combustion. The more greenhouse gases are sent into the atmosphere, the bigger the impacts.

By late in the 21st century, some climate models indicate that the amount of west-side forests that will burn in an average year will be more than double that of the last half of the 20th century. And, in any one particular patch of forest, fire is expected to make more rapid returns than in past centuries.

It remains unclear just how the west-side forests will be reshaped by this warming world.

Harvey hopes that the Norse Peak study sites can be used to launch a decades-long monitoring effort to help answer the question.

“I’m still early in my career,” Harvey said. “This is a really unique opportunity to look one, 10 and 30 years down the road and track this system as it’s changing.”